The crushing defeat of Nova Scotia's NDP government has dealt a blow to Thomas Mulcair just as Parliament is set to resume next week.

But the federal NDP Leader says there are lessons to be learned from the Nova Scotia debacle – and from an earlier disappointing loss in British Columbia – that could ultimately benefit the national party.

"There's always a silver lining even in these very dark clouds which can give you information about how better to prepare," Mulcair told the Canadian Press on Wednesday.

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"I know I'm going to be facing a very tough adversary in [Prime Minister] Stephen Harper."

Since becoming leader 18 months ago, Mulcair has repeatedly pointed to the success of provincial New Democrat governments to bolster his argument that the NDP can do the same federally.

Indeed, he staged a "leader's summit" last January to bask in the reflected glory of two NDP premiers – Nova Scotia's Darrell Dexter and Manitoba's Greg Selinger – as well as other provincial NDP leaders, at least one of whom, British Columbia's Adrian Dix, seemed poised at the time to join the ranks of first ministers.

"That's precisely the point," Mulcair said candidly, when asked if he was "borrowing a little of their success provincially."

But fate has not dealt kindly with provincial New Democrats since then. Dix resigned after the NDP failed to win B.C.'s election in May, confounding public opinion polls which had predicted an easy victory over Christy Clark's Liberals.

And on Tuesday, Dexter lost his own seat as his one-term government was reduced to third-party status.

Polls suggest Selinger's government is also in trouble, although he has plenty of time before the next Manitoba election in 2015 to turn that around.

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"Darrell Dexter did an amazing job," Mulcair insisted.

"He did what he could to save jobs as companies were trying to fold, he did what he could to clean up the books of the province, he took some tough decisions and he paid a heavy price for it at the polls."

Justin Trudeau was the only federal leader to campaign in Nova Scotia but Mulcair doubted the popular Grit leader had much to do with the provincial Liberals' landslide victory.

"He didn't turn up in British Columbia so I don't think that you can necessarily make a cause-to-effect relationship between any individual there."

Mulcair said federal strategists have "sifted through the debris field" of B.C. and learned some important lessons on "everything from how you organize the ridings to how you approach different stakeholders to how you keep a consistent message throughout the campaign." Dix's mid-campaign flip-flop on the Kinder Morgan pipeline proposal didn't go over well, he noted.

In Nova Scotia, Mulcair said it appears that Dexter's efforts to clean up the government's books appear to have been "too constraining" for voters' tastes.

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Despite the election losses provincially, Mulcair indicated he'll continue to make the case that New Democrats have proven to be the most fiscally prudent administrators of any party in the five provinces and territories where they've formed government.

In a postmortem of the B.C. election, NDP campaign director Brian Topp concluded that the party should have behaved more like Harper's Conservatives: limiting media access to the leader, constantly repeating simple messages, aggressively attacking the opposing leader's record and weaknesses.

Mulcair said he hasn't read the postmortem by Topp, his erstwhile federal leadership rival, but he has no intention of engaging in personal attacks on his opponents.

"Does that mean we don't go after the other guy's record? Heck, no," he added.

He promised "knock-down, drag-out fights on policy and proposals" and the ethical lapses of both Conservatives and Liberals. And he gave a sample of that with a broadside at Harper.

"I've never underestimated Stephen Harper and I've seen by his repeat behaviour in cheating in elections, whether it was the in-and-out scandal, whether it was the robo-calls, they don't have any ethics when it comes to elections," Mr. Mulcair said. "So we know that we're going to be preparing and steeling for a very serious fight with the Conservatives in the next campaign."

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It's not just provincial New Democrats who are causing Mulcair grief these days.

Quebec's Parti Québécois government has planted another potential landmine for him: its proposed charter of Quebec values, which would prohibit public servants from wearing prominent religious symbols.

Mulcair has come out strongly against the charter, even though polls suggest it's particularly popular among rural francophones who voted for the NDP in droves in 2011.

The PQ is reportedly considering watering down the charter but Mulcair indicated Wednesday he's unlikely to tone down his opposition to it, regardless of the potential impact on the NDP's Quebec base.

The charter is out of sync with "the real Quebec values" of "tolerance, inclusion, openness and egalitarianism," he said, adding that it's given the province a black eye in the rest of the country.

"It's going to have a regrettable echo for a long time to come … I think anybody who panders to the lowest common denominator on these issues is going to pay a price for it long term."

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